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dicepro: The doubling cube is an integral part of backgammon - multipoint matches are required there to eliminate the luck factor. And, quite importantly, backgammon doesn't have a draw. Furthermore, a backgammon game counts for 1, 2 or 3 points depending on the board situation when the game ends.
This is not the situation with most other games (except for the "draws are not possible" in some games). A doubling cube just doesn't make sense for the other games.
There are many things that could be implemented to speed up games: autopass and autoplay (and then implemented in a useful way, not as done currently), and public shaming of people who play on (delaying their moves consistently till a few hours before their time runs out) in a hopelessly lost situation.